The processing of semiconductor substrates is integral to the manufacture of integrated circuits. Most commonly, these substrates are in the form of silicon wafers that are five to eight inches in diameter, although a variety of other substrates of various sizes are also known. A single wafer can be exposed to a number of sequential processing steps including, but not limited to, chemical vapor deposition (CVD), physical vapor deposition (PVD), etching, planarization, and ion implantation.
The use of robots has become standard in semiconductor processing. Robots can process a large number of substrates through many different processing technologies, and can perform repetitive tasks quickly and accurately. The use of robots thus eliminates human fatigue and minimizes operator errors as factors in the fabrication process.
Most modern semiconductor processing systems include robotic cluster tools that integrate a number of process chambers together in order to perform several sequential processing steps without removing the substrate from the highly controlled processing environment. These chambers may include, for example, degas chambers, substrate pre-conditioning chambers, cooldown chambers, transfer chambers, chemical vapor deposition chambers, physical vapor deposition chambers, and etch chambers. The combination of chambers in a cluster tool, as well as the operating conditions and parameters under which those chambers are run, are selected to fabricate specific structures using a specific process recipe and process flow.
Once the cluster tool has been set up with a desired set of chambers and auxiliary equipment for performing certain process steps, the cluster tool will typically process a large number of substrates by continuously passing them, one by one, through the chambers or process steps. The process recipes and sequences will typically be programmed into a microprocessor controller that will direct, control and monitor the processing of each substrate through the cluster tool. Once an entire cassette of wafers has been successfully processed through the cluster tool, the cassette may be passed to yet another cluster tool or stand alone tool, such as a chemical mechanical polisher, for further processing.